Two screening methods are to be employed to assess the SAR of polycarboxyl molecules for binding to the surface of HA (hydroxyapatite). The methods include dye adsorption interference and titration with acid. Molecules to be studied are analogues of known complex formers, mellitic and citric acids. Those molecules found to adsorb to the surface of HA will be studied further by infrared techniques. The study will aid in evaluating the property (both useful and deleterious) of potential binding to HA drug molecules. The ability to bind cations in general and Ca in particular, in solution does not always coincide with the ability of ligands to bind to Ca in a crystalline surface. This study will provide comparative data on the binding by HA of various polycarboxylate ions on the basis of their structure.